The present invention relates to an ink printer equipped with a carriage movable along a record carrier and, in particular, to an ink printer in which an ink printing head and an intermediate container are mounted on the carriage.
In the operation of ink mosaic printers, it is necessary to supply ink continuously to the printing head. This is accomplished in known apparatus by placing an ink reservoir at a stationary location near the printer and by mounting the printing head on a carriage which moves along the line being printed. Ink is fed through a flexible tube from the reservoir to the printing head.
This arrangement has the advantage that the reservoir can have a relatively large capacity without the moving printing head being subjected to a significant additional load. However, with the rapid carriage accelerations and decelerations inherent in an ink printer, pressure and suction surges occur in the flexible line, and these surges are transmitted to the printing head. As a result, there is interference with the formation of the ink drops and impairment of the quality of the printed material. Such malfunctions may also cause interruptions in the operation of the printing head.
To overcome such difficulties, the ink reservoir may be carried on the printing head as it travels along the printed line on the record carrier, as disclosed in U.S. Pat. No. 3,967,286. However, with this arrangement, the inertial masses that must be accelerated and decelerated alternatingly on the carriage during the printing process are increased, and these inertial masses change as the ink reservoir is depleted so that different acceleration and deceleration conditions exist depending upon the amount of ink in the reservoir. Accordingly, the ink reservoir carried along with the printing head must be relatively small.
U.S. Pat. No. 3,771,165 discloses an ink supply for an ink printer wherein the printing head is supplied with ink from a stationarily mounted ink vessel connected by a flexible line to an auxiliary reservoir mounted on a movable pen-carriage of a recorder. However, the auxiliary reservoir is not a storage vessel but rather functions as an attenuation chamber. In supplying curve recording devices, this arrangement sufficiently attenuates pressure and suction surges during acceleration and deceleration but does not absorb increases or decreases in pressure of longer duration; that is, the patented arrangement does not relieve the printing head of movement-dependent changes in pressure.
Likewise, in German Offenlegungsschrift No. 2,336,485 an ink printer is disclosed which has a stationary primary ink reservoir. When the printing head is at one end of the line being printed, the primary ink reservoir is connected by a plug-in coupling to an intermediate reservoir disposed at the printing head and moving with it along the printed line. By means of a valve system, the ink supply required for at least one line is transferred under pressure from the stationary ink reservoir to the intermediate reservoir. Since the amount of time available for replenishing the ink in the intermediate container is relatively short during the regular printing operation, the ink transfer can take place only at a very high ink pressure. This high ink pressure is propagated into the region of the printing head and has an adverse effect on the operation of the printer.
German Offenlegungsschrift No. 2,742,633 discloses a vessel having a cavity containing an elastic membrane which subdivides the vessel into two chambers. One of the chambers contains an ink-filled bag which is provided with a connecting pipe stub forming a passage for the ink. The other chamber is in communication with the atmosphere via an opening in the vessel housing. This vessel permits pressure equalization between the cavity and the surrounding atmosphere and in the event of a leak, prevents the escape of ink through the air hole. However, the vessel is not suitable for use on a moving carriage nor is it provided with means for attenuating and controlling a replenishing pump.
It is an object of the present invention to provide an ink printer having an exchangeable printing head and an intermediate ink container disposed on a movable carriage. The intermediate ink container is in flow-connection with the printing head so that an automatic and free replenishment of ink is obtained. The ink, which is free of gas bubbles, is transferred through an inlet channel from a stationary reservoir.